The invention relates to sewing apparatus, more especially a contour sewing machine for a sewing unit, comprising a vertically reciprocating needle and a holder of material for sewing movable relative thereto which, in order to make a seam having a predetermined shape, is movable in two directions at an angle to one another in a plane, the movements being generated by two independent motors and the holder being releasably connected to a bearer driven in one direction and coming into engagement with a drive operating in the other direction.
DE 21 64 151 A1 (corresponding to U.S. Pat. No. 3,752,058) describes a sewing installation wherein the holder of material for sewing is mountable on a slide. The slide is permanently connected to a belt rotating in a horizontal plane. The belt is mounted on a bearer disposed so as to be movable in the longitudinal direction of the sewing machine (the Y direction) transversely to the driven direction. The connection between the holder and the slide can be electromagnetic. The holder and the material for sewing which it carries is fastened on the slide in front of the sewing machine, conveyed in the transverse direction (the X direction) through the stitch-forming region of the sewing machine, and removed behind the sewing machine.
One disadvantage of this sewing installation is that the slide must be moved back each time after reaching the place where the material for sewing is removed, so as to be loaded with another holder. The idle travel increases the cycle times of the machine and seriously affects the production costs in the clothing industry. In addition, heavy masses have to be moved in reciprocation, which means that the motor driving the slide must be designed correspondingly and thus increases the cost of producing the sewing installation.
A sewing installation according to the preamble is known for example from DE 39 38 819 A1 (corresponding to U.S. Pat. No. 5,127,348). In this sewing installation the holder is moved through the stitch-forming region of a stationary sewing machine. The holder is positively connected to the bearer via a toothed drive. The toothed drive comprises a pinion or a rotating toothed belt and a rack for connecting thereto and provided on the holder. The positive connection is produced by a guide block mounted for pivoting on the bearer and comprising a number of rollers which can be mounted on the rack of the holder and thus guide the holder in the transverse direction (the X direction).
With regard to the transverse direction, the holder as before is inserted into the sewing installation in front of the stitch-forming region and removed behind the stitch-forming region. In order to convey the holder from the place of insertion to the place of removal, a very long rack is needed. This results in a very long transit time for the holder. Since the length of the rack depends on the distance between the place of insertion and the place of removal, the holder, independently of the size of the articles for sewing, must be equipped with racks of the same length, which in principle can be considerably longer than necessary for the size of the actually required holder, the result being idle travel over relatively long distances and affecting the economics of the sewing installation. To obtain a high-quality seam, the toothed drive must be accurately made. The accuracy requirements result in relatively high production costs, in addition to the weight of the holder resulting from the rack. In order to limit the production cost, attempts are made to reduce the distance between the places of insertion and withdrawal of the material for sewing to a minimum. The result is that a new holder cannot be inserted until the previous holder has been removed, which likewise affects the economics of the sewing installation. Additional time is lost because of the required accurate positioning when the holder is inserted, so that the seam can be formed at the right place.
Another disadvantage of this sewing installation is that the operator manipulating the holder needs to pay special attention in order not to damage and not to be injured by the rack, which must be made of metal for strength.
DE 39 32 226 A1 discloses a sewing installation comprising an X-Y cable device comprising a guide rail provided on a movable part connected to the holder. The guide rail can be moved relative to guide blocks 17 connected to the unit for driving the holder in the longitudinal direction. This retains its degrees of freedom when the holder is moved in the transverse direction.
DE 38 19 136 C2 describes a sewing unit wherein the holder can be moved by a conveying device between a loading station and the sewing machine. The conveying device has a control-lever transmission system mechanically guided in a guide connected to the drive device and associated with a compensating mechanism.
Starting from this problem, the aim is to improve the sewing apparatus described hereinbefore, a special aim being to increase the output and reduce the cost of producing the insertable holder.
Accordingly, the present invention is directed to sewing apparatus as set out in the opening paragraph of the present specification, in which the holder is mountable via a bearing thereon on a guide rod connected to a fixed place on the bearer and is connectable by at least one connecting element to the drive for the other direction, which coincides with the direction in which the guide rod extends.
As a result of this construction the holder can be inserted and removed at various positions, so that the holders can if required be inserted without spaces between them, thus practically avoiding idle times and appreciably increasing the cycle times of the machine as compared with the prior art. Since the holder does not need a rack and the connecting element for the drive can be made relatively small and low-weight, the holder can be economically produced and its drive can be made correspondingly small. The holder only has to be mounted on a guide rail, where it stays owing to gravity, and the result is that the machine is simpler to operate, since there is no need of time-consuming positioning and locking.
Preferably the holder is mounted on the guide rod via at least one bearing having a substantially U-shaped cross-section and also constituting the only connection to the guide rod. The bearing can be in the form of a simple recess provided in the holder. The recess can be adapted to the contour of the guide rod, resulting in a positive connection.
Advantageously two bearings are provided. These can be disposed on the outer sides of the holder, so that guidance is reliable and the holder cannot become crooked.
Advantageously the connecting element is in the form of a toothed pin and the drive for the transverse direction comprises a rotating toothed belt cooperating therewith. The holder will then be entrained via the pin, which is inexpensive to produce. Alternatively the connecting element can be a toothed segment which engages in the toothed belt.
The toothed belt preferably rotates in a vertical plane. The teeth can therefore be formed on the upper surface, and the tolerance for the arrangement of the connecting element on the holder is increased if the belt is made correspondingly wide. This feature ensures that the holder is connected to its drive by gravity immediately after insertion (placing on the guide rod).
Alternatively the guide rod can be a spindle driven in rotation. It will then also form part of the drive for the transverse direction and can be directly driven by a motor. This enables the number of components to be reduced, since the toothed belt can be omitted. In that case advantageously the holder is supported via a cam engaging in the spindle.